Habitat for Humanity is a global nonprofit with a presence in nearly 1,400 communities throughout the US. The organization works to strengthen and stabilize families and communities by providing housing for those in need. Often, these homeowners help build their own houses alongside volunteers, and pay an affordable mortgage.
The Puget Sound region, or greater Seattle/Tacoma area, is home to several Habitat for Humanity (Habitat) communities. The newest of these is still under construction. The small, partially-wooded development in Midland, WA, grows by about a half-dozen houses each year.
The Woods at Golden Given or “The Woods,” as it’s called, is comprised of single-family homes between 1,100 and 2,000 square feet, each with a small yard and centralized parking. A community building, playground and basketball court fill the middle of the rectangular subdivision.
But, unknown to visitors, the quaint neighborhood was also host to an in-depth energy use study that changed the Washington State Energy Code last year.
While working with the local utility, Tacoma Power, Habitat managers decided to install a hybrid electric heating system; zonal electric (either baseboard or fan-forced wall heaters) and a 12,000 BTU ductless mini-split in each home. Habitat for Humanity knew upfront that the 30 houses would all be built to meet the insulation requirements of the Washington code, and would also be equipped with heat recovery ventilators (HRV).
Tacoma Power research
“We wanted to use The Woods as an opportunity to study the impact of high-efficiency ductless heat pump technology on the power consumption of an electric-resistance heated home,” said Bruce Carter, assistant conservation manager at Tacoma Power. “So we essentially designed an experiment that would span two years, in which the home would automatically switch from all resistance heat to a hybrid system that included a mini-split.”
Before the project broke ground in 2013, Habitat, through a suggestion from Johnstone Supply, approached Alpine Ductless, LLC, Olympia, Wash., for a proposal to install mini-split units in each home as they were built over the next few years.
As the name suggests, Alpine Ductless installs and services mini-split systems only, though the applications can get very large and complex.
“Because of the hydroelectric dams on the Snake and Columbia Rivers, the Puget Sound area has always had cheap power,” said Cory Eckert, co-owner of Alpine Ductless. “As a result, there’s a lot of zonal-electric heating here, probably more than anywhere else in the country. So we were excited to be involved with this project from the beginning, despite the unconventional installation arrangement.”
For Eckert, the job didn’t result in quite as much work for his installers as a typical project would. Alpine Ductless supplied 29, 12,000 BTUH Fujitsu RLS2 mini split systems in 2013. The mini-split units were placed in storage when construction began, and are pulled out and installed as the homes are built.
Habitat employees or volunteers hang the wall-mount units and set the condensing unit. Their electrician also completes the wiring. At that point, Eckert’s crew arrives onsite to install and vacuum down line sets and commission the systems.
The Tacoma Power experiment began with commissioning of the first unit, and finished the test with about 13 houses in 2016 with 20 homes complete.
“We’ve installed three different ductless brands, but I think Fujitsu is the leader in innovation,” said Eckert. “We also get great support from Curt Kanemasu, at manufacturer’s rep firm Cascade Products.”
Gathering data
Before the first unit was installed, Tacoma Power’s Carter looked to Kanemasu for specific performance and efficiency information about the Fujitsu units. They also discussed how to control the two heating systems in order to gather the energy data needed.
Carter also consulted with Washington State University Energy Program staff on data monitoring strategies. Ultimately, WSU-EP was brought in as a partner to do installation and monitoring of data logging equipment as well as independent evaluation of the energy data.
“To facilitate switching between operation modes, each home used a two-channel time clock that switched between the electric resistance heaters in the main living area and the heat pump,” explained Carter. “The resistance heaters in the rest of the house remained ‘hot’ all the time.”
The time clock energized either the electric resistance heaters or the mini-split in the living room on sequential weeks. Monitoring was conducted through a series of current transducers, data loggers and temperature sensors that captured electrical consumption on each circuit, indoor and outdoor temperature, and the heat pump’s line set temperature.
Data loggers also tracked temperature in the perimeter bedrooms to gauge the impact of the heat pump on tempering of these zones.
The collection of data took place only during the heating season. During the summer, the mini-splits provide air conditioning for all homes, aided by the Fantech Flex 100 HRV systems.
The HRV not only serves to provide efficient, healthy ventilation, but also distributes either tempered air throughout the structures.
“What we found was that the houses at The Woods used between 40 and 48 percent less power in hybrid heating mode,” continued Carter. “We also found that, from a comfort standpoint, homeowners preferred the heat pump over the baseboard or wall heaters.”
Changing legislation
“We took that information and integrated it into the Washington State Energy Code cycle,” said Carter. “We were successful and, as of July 1st, 2016, all new, zonal-electric heated homes in the state of Washington – not just Habitat homes - are required to have a ductless heat pump in the main living area.”
Eckert explained that in a home with higher infiltration rates, or with a higher heating load in general, the results would likely be even more impressive.
“The exciting thing about being a part of this study was to realize that as a company we really are saving a lot of power versus homes that use zonal heating exclusively,” said Eckert.
“We’re able to quickly install these units, offset the customer’s power consumption, and make them extremely comfortable,” he added.
Alpine Ductless has installed mini-splits at more than 1,400 homes that are heated with electric power. He estimates that, if they’ve saved each of those customers an average of 47 percent of their power during heating season, that’s enough power savings to supply all the power needs of a 650-lot subdivision of 1,200 square-foot homes.
“As the company owner, that makes it really easy to sleep at night,” said Eckert. “And I’m confident that I speak for the whole company when I say that.”